Amphistomy increases leaf photosynthesis more in coastal than montane plants of Hawaiian ʻilima

Premise of the study
The adaptive significance of stomata on both upper and lower leaf surfaces, called amphistomy, is unresolved. A widespread association between amphistomy and open, sunny habitats suggests the adaptive benefit of amphistomy may be greatest in these contexts, but this hypothesis has not been tested experimentally. Understanding amphistomy informs its potential as a target for crop improvement and paleoenvironment reconstruction.
Methods
We developed a method to quantify \"amphistomy advantage\", AA, as the log-ratio of photosynthesis in an amphistomatous leaf to that of the same leaf but with gas exchange blocked through the upper surface (pseudohypostomy). Humidity modulated stomatal conductance and thus enabled comparing photosynthesis at the same total stomatal conductance. We estimated AA and leaf traits in six coastal (open, sunny) and six montane (closed, shaded) populations of the indigenous Hawaiian species ʻilima (Sida fallax).
Key results
Coastal ʻilima benefi..., Plant sampling and climate
 
We identified 7 suitable natural populations of ʻilima on Oʻahu and 5 on Hawaiʻi Island by consulting Yorkston and Daehler (2006) and citizen scientist records on iNaturalist (Anon, 2022). We avoided sites that appeared to be cultivated. We visited sites between August and November 2022. For logistical reasons, the sites on Hawaiʻi were sampled during one three-day trip. We haphazardly sampled eight plants distributed evenly between the highest and lowest elevation plants along a transect at each site. For safety and conservation reasons, transects were along a trail or road. We did not sample small individuals if there was risk removing leaves would cause mortality. From each plant, we collected two fully expanded leaves for trait measurements. We sampled stomatal traits on all leaves; leaf thickness on one leaf from three randomly selected plants per site; and, due to limited time, a single leaf from a single plant at the middle of each transect for gas ex..., , # Data from: Amphistomy increases leaf photosynthesis more in coastal than montane plants of Hawaiian ʻilima (*Sida fallax*)

This dataset contains leaf trait data for each individual 'ilima individual and/or leaf in our sample.

## Description of the data and file structure

The data are structured as a comma separated value (CSV) file with 185 rows and 27 columns:

* `genus`: genus name
* `species`: specific epithet
* `authority`: authority
* `exposition`: sampled from 'natural environment' or 'experimental growth conditions'
* `plant_maturity`: 'juvenile' or 'mature' plant
* `leaf_age`: 'young', 'youthful', 'mature', 'old', or 'senescent' leaf according to [Bowman and Box 1983](https://doi.org/10.1111/j.1442-9993.1983.tb01515.x)
* `site`: freeform site name
* `site_code`: four-letter site code
* `site_type`: 'coastal' or 'montane' site type
* `island`: island where site is located (oahu = O'ahu; hawaii = Hawai'i, aka Big Island)
* `latitude_degree`: approximat...